It has been determined that premature infants have a greatly decreased lactase activity until approximately thirty-six weeks of gestation when there is a rapid increase to newborn levels, as described in Kien, C. L.: Colic Fermentation of Carbohydrate in the Premature Infant: Possible Relevance to Necrotizing Enterolcolitis. J. Pediatr. 117 (suppl): S52-S58, 1990. Past and current infant formulas designed for premature infants contain lactose at levels of at least 40% lactose, such as present in Enfamil.RTM. Premature Formula (Mead Johnson Nutritionals, Evansville, Ind., U.S.A.). The remainder of the carbohydrate fraction is typically available in the form of glucose polymers. With the low amounts of lactase present in the immature intestine of premature infants, there may be excess carbohydrate whose fermentation results in the formation of hydrogen gas and possible development of pneumatosis intestinalis, the pathologic hallmark of necrotizing enterocolitis.
In addition, premature infants frequently have episodes of feeding intolerance possible secondary to lactose intolerance. During these episodes, neonates present with abdominal distension, gastric retention of feedings, diarrhea, and sometimes guaiac positive stools, as described in Walsh, M. C., Kleigman, R. M.: Necrotizing Enterocolitis: Treatment Based on Staging Criteria. Pediatr Clin North AM 33:179-201, 1986.
Alternative infant formulas designed specifically for premature babies are needed.